1) Field of the Invention
The present invention relates to a gravity-feed chute-rack storage system which is installed in the neighborhood of automotive or electric production lines and permits relatively lightweight assembly parts shelved to be selectively picked up.
2) Description of the Prior Art
While gravity-feed flow-rack storage systems making use of plastic conveyor rails are mainly employed in the industrial world, chute-rack units have recently become known in view of cost-saving as those for use in making lightweight, relatively large bare parts flow on production lines, thus dispensing with not only containers themselves but also the step of recovering them. A chute-rack unit of the sort that utilizes rack rails is formed with thin-wall steel pipes sheathed in a plastic resin material having excellent sliding properties (Japanese Utility Model Laid-Open No. 169518/1989).
More specifically, the chute-rack unit is formed by uprightly setting two square, side frames adequately spaced apart, the side frame being formed with a thin-wall steel pipe sheathed in a plastic resin material, for example. The top and bottom parts of the side frames are coupled together with a plurality of horizontal coupling members similar in structure to the pipe mentioned above to form a chute-rack unit. Moreover, a multi-tier rail supporting members similar in structure to the pipe is horizontally fitted onto the front, intermediate and rear sides of the chute-rack unit. Between the rail supporting members are rack rails in the form of two pairs of chute pipes, each being formed with a thin-wall steel pipe sheathed in a plastic resin material of such as high-density polyethylene or nylon having good sliding properties. Further, the pairs of chute pipes are tilted forward and adequately spaced apart to prevent stock (parts to be assembled) from falling therethrough.
Notwithstanding, there may arise inconvenience in that the number of shelves has to be reduced, thus decreasing stock efficiency, because a gradient of 10.degree.-15.degree. is required for the chute-rack unit above to let relatively heavy articles of stock slide smoothly thereon and 15.degree.-30.degree. to let single lightweight bare articles of stock slide likewise in comparison with a gradient of 3.degree. or thereabout in the case of plastic conveyor rails, though the conventional chute-rack unit is advantageous in cost to what employs the plastic conveyor rails.
On the other hand, the sliding performance of stock may be reduced as the gradient of each rack rail is decreased in order to increase stock efficiency. In other words, the worker involved in taking out stock is compelled to make waste moves, which will also result in reducing workability, as he is supposed to swing the whole chute-rack unit from the unloading port, hook the stock by means of a bar or otherwise making a supplier of the stock use a rod to push the stock.